12D.3
Tropical cyclone extratropical transition: A reversible process?
John L. Beven II, NOAA/NWS/NCEP/TPC, Miami, FL
Recent studies of the transition of tropical cyclones to extratropical cyclones have covered various aspects of the issue, including climatology, evolution of cyclone structure, and changes in intensity and precipitation patterns. Operational experience and other studies have shown that extratropical cyclones can evolve into tropical cyclones. Both transitions offer considerable challenges to forecasters. Additional challenges comes from cyclones that begin a transition process and fail to complete it. While this most frequently happens for extratropical cyclones trying to become tropical, it also has occurred for tropical cyclones trying to become extratropical.
This paper will show satellite data, surface analyses and model data documenting the evolution of three Atlantic tropical cyclones that began the process of extratropical transition and failed to complete it - Dennis (1999), Alberto (2000), and Gabrielle (2001). Dennis and Alberto interacted with baroclinic zones with the resulting ingestion of cooler, dryer air and loss of the associated convection. However, both cyclones eventually regained full tropical cyclone characteristics, indicating that the process of extratropical transition is reversible under the right atmospheric and oceanic conditions. Gabrielle also interacted with a baroclinic environment, losing much of its tropical cyclone character in the process. In contrast to the other examples, however, Gabrielle?s failed transition resulted in the formation of a warm-core hybrid cyclone rather than a classical tropical cyclone.
Session 12D, tropical cyclone extratropical transition (Parallel with Sessions 12A, 12B, and 12C)
Thursday, 2 May 2002, 8:30 AM-10:30 AM
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